Ok, here's a sort of wild idea, and stop me if this has been done already. But how about someone design some kind of LAMP application interface with a trimmed down phpMyAdmin, a simplified Apache, WebUI (maybe firefox based?), a trimmed down MySQL (or equivalent light weight database) with full support for Javascript, PHP, and other things.

In short the idea is to have something separate from the web browser that takes one particular bundled module (php scripts + database + ui xhtml code all in one zip file) and runs it like you would see it on the web, but as an application instead. It's an idea that's probably already been suggested and subsequently blown out of the water, but since I didn't see anything with this specific setup mentioned, I figured to broach the question.